package DemoText;

/**
 * z字形变换
 */
public class LeetCode6 {
    public String convert(String s, int numRows) {
        if (numRows == 1) return s;
        int d = numRows * 2 - 2;
        int n = s.length();
        StringBuilder ret = new StringBuilder();
        for (int i = 0; i < n; i += d)
            ret.append(s.charAt(i));
        for (int k = 1; k < numRows - 1; k++) {
            for (int i = k, j = d - i; i < n || j < n; i += d, j += d) {
                if (i < n)
                    ret.append(s.charAt(i));
                if (j < n)
                    ret.append(s.charAt(j));
            }
        }
        for (int i = numRows - 1; i < n; i += d)
            ret.append(s.charAt(i));
        return ret.toString();
    }
}
